Icon size

It won't matter what iOS version. Display Zoom is not supported on iPhone X. See:

https://support.apple.com/en-ie/guide/iphone/aside/iph077d2b9f5/13.0/ios/13.0

While icon size on iPhone X cannot be changed, you can try utilise some of great accessibility features. For instance, Zoom:

https://support.apple.com/en-ie/guide/iphone/iph3e2e367e/13.0/ios/13.0

So. When you go to Settings > Display & Brightness and you swipe that page upwards, towards the bottom of that page you don't have as the last item on that page, Display Zoom and just below the option to tap View, which gives you Standard or Zoomed?

Settings > Display & Brightness > View > Zoomed

What iOS version are you running on your iPhone X? Settings > General > About > Version

Thanks. It's been a while since I had iPhone X, so wasn't considering this.

As iW00 correctly posted, it's not an available option on iPhone X. It is available on Xs Max.